1. Field of the Invention
This invention relates to ventilation systems and particularly but not exclusively to ventilation systems for commercial kitchens.
2. Related Art
Ventilation systems are usually required in commercial kitchens to remove smoke, smells and other unwanted airborne or gaseous substances. Typical systems comprise an extractor fan, the inlet to which is located as close as possible to the source of the smoke etc. in an attempt to prevent it from coming into contact with staff working in the kitchen, and an air supply to replace the extracted air with fresh air. A large canopy is provided above the appliance or appliances which are a potential source of smoke etc. Air and smoke etc. is removed from the canopy via an outlet provided at an upper region of the canopy. Such canopies should ideally be as large as possible in order to maximise the capture of the smoke etc. which may drift not only upwards, but also sideways. The canopy therefore takes up a large space, which is particularly inconvenient in smaller kitchens. Furthermore restrictions are placed on the minimum height of the lower edge of the canopy above the floor, in order to provide adequate headroom for staff and this means that, particularly where a kitchen has a low ceiling, the canopy is restricted as to how deep it may be and therefore how effectively it may capture the smoke.
With the known ventilation systems, in order to obtain adequate smoke extraction it is generally necessary to employ large and noisy extractor fans. These consume a lot of power and require correspondingly large ducting which is bulky and can be difficult to accommodate where space is restricted. Even with large canopies and high air extraction rates, known ventilation systems are not completely effective in removing smoke etc. from the kitchen.